Production of lubricating oils by catalytic hydrogenation



United States Patent 3,189,540 PRODUCTION OF LUBRICATING OILS BYCATALYTIC HYDROGENA'HGN Robert H. Kozlowski, Berkeley, and Robert L.Jacobson,

Pinole, Califi, assignors to California Research Corporation, SanFrancisco, Calif.," a corporation of Delaware No Drawing. Filed Jan. 2,1962, Ser. No. 163,923

1 4 Claims. (Cl. 208-464) This application is a continuation-in-part ofcopending application SerialNo. 12,319, filed March 2, 1960, now US.Patent No. 3,114,701.

' This invention relates to the production of lubricating oils bycatalytic hydrogenation, and in particular the invention relates to theproduction of lubricating oils of improved color by catalytichydrogenation of petroleum oils rich in polycyclic hydrocarbons andcontaining nitrotion controlled to remove a specified fraction of thenitrogen compounds, using certain high metal content, sulfided,nickel-molybdenum-alumnia catalysts. Still more particularly, theinvention relates to an improved process using relatively severeconditions of catalytic hydrogenagen content of a petroleum oil andthereby to obtain a lubricating oil product of improved properties.

The use of catalytic hydrogenation in the refining of lubricating oilsis well known. Mild hydro-finishing has been employed as a substitutefor acid treating or clay contacting of refined lube oils, usingrelatively mild conditions of low temperature, low pressure, and highspace velocity. Destructive hydrogenation has also been proposed as asubstitute for solvent extraction of crude lube molybdenum, on alumina,at 1000 p.s.i.g., 600

- content sulfided' catalysts;

tained at more'severe conditionsof elevated temperature "and pressureand'low'space velocity. v

oils, using severe conditions of high temperature and pressure. Thecatalysts employed in the prior art processes are usually eitherhydrofining catalysts such as molybdenum oxide, cobalt, molybdate,nickel-tungsten sulfide, etc., or hydrogenation catalysts, such asnickel or platinum. Usually the catalyst metals, oxides, or sulfides,are supported on -a carrier such as alumina, silica-alumina, ormagnesia. The supported hydrofining catalysts have invariably a lowmetal content of less than by weight.

Ne have found that certain high metal content sulfidednickel-molybdenum-alumina catalysts give outstanding results in thecat-alytic'hydrogenation of petroleum oils rich in polycyclichydrocarbons, particularly with respect to producing lube oils ofimproved color. Thus, for example, when a bright stock (187 SSU at 210F.) was subjected to catalytic hydrogenation by contacting with a priorart hydrofining catalystcontaining 2.8% cobalt and 6.7% F., and 0.5volume of oil per volume of catalyst per hour .(LHSV), with 2000 s.-c.f.of H per barrel of oil,the ASTM color was improved from 8 to 6.5. When asulfided 6% nickelmolybdenum, on alumina, catalyst was used at the sameconditions, the ASTM color wasimproved from 8 to 5.5. At greaterseverity, for example, 650 F. and with other conditions comparable,product color improved even more, from 8.0 to 3.5, with the sulfidedNi-Mo catalyst. Similar superior results are obtained in the catalytichydrogenation of distillate lube oils with'the high metal Also, evenbetter color is ob- The high metal content sulfidednickel-molybdenumalumina catalysts used in contain 340% by weightmolybdenum, with the more active catalysts containing 4-l0% nickel andl5.5% molybdenum. ratio of nickel to molybdenum is in the range of 0.25to 0.8, preferably about 0.6. A typical preferred catalyst will containabout 6 weight percent nickel and about 20 weight percent molybdenum.The catalysts may be prepared by alternate impreguation of a supportconsisting essentially of alumina, calcining titer each impregnation theprocess of this invention nickel and 1230% by Weight The atomic toconvert the metal compounds to the metal oxides; or they may be preparedby simultaneous coprecipitation of aluminum, molybdenum, and nickelcompounds; or by coprecipitation of aluminum and molybdenum compoundsfollowed by impregnation with nickel, and with additional molybdenum, ifdesired. The catalysts are sulfided before use in the process. A specialproperty of these catalysts when sulfided is their unusually highactivity for the removal of nitrogen from petroleum oils containingnitrogen compounds by catalytic. hydrogenation of the Thus, for example,the

nitrogen compounds to ammonia. catalysts are found to be from two tofive times as active as prior art hydroiining catalysts for the removalof nitrogen from neutral distillate lube oils. The catalysts, theirpreparation, and their use in processes for the substantially completeremoval of nitrogen from distillable hydrocarbon oils are disclosed inour pending applications Serial Nos. 12,319, filed March 2, 1960, nowUS. Patent No. 3,114,701; 12,466, filed March 2, 1960, now abandoned;and 90,382, filed February 20, 1961, now abandoned,

in accordance with the catalytic hydrogenation process of thisinvention, a petroleum oil rich in polycyclic hydrocarbons andcontaining nitrogen compounds is hydrogenated by contacting with a highmetal content, sulfided, nickel-molybdenum-alumina catalyst containing3-l0 weight percent nickel and 1230 Weight percent molybdenum, in thepresence of excess hydrogen at a partial pressure of over 800 p.s.i.a.,at 600800 F., and 0.2-3 LHSV. The hydrogen partial pressure,temperature, and space velocity are controlled within the foregoingranges to remove a specified fraction of the nitrogen content of theoil. When the conditions are so controlled, the degree, fraction orpercent nitrogen removal from a petroleum oil is found to be a directindex ofthe degree of change in color and certain other properties ofthe oil which reflect the hydrogenation of unsaturated and unstablecompounds therein. The lube oil properties found to be so related to theextent of hydrogenation in terms of nitrogen removal are-expressed insomewhat arbitrary measurements, in particular: color, viscosity, pourpoint, oxidation stability, and additive response. Improvement to adesired extent of at least one lube oil property, in addition to color,selected from the group consisting of viscosity, pour point, oxidationstability, and additive response, is achieved by controlling theconditions to obtain from 30 to percent nitrogen removal .in thecatalytic hydrogenation process of this invention. 7

Preferred lubricating oils areessentially naphthenic in basic structure,and have alkyl substituents ofvarying complexity. Essentially parafiinicor waxy hydrocarbons are not desired, nor are essentially aromatichydrocarbons, because of their poor lubricating properties. Hence, thepetroleum oils from which lubricating oils are produced by thisinvention are petroleum oils rich in polycyclic hydrocarbons, and whichcontain nitrogen compounds. Predominantly parafiinic petroleum oils arenot suitable feed stocks for the process because such compounds are notconverted to the desired naphthenes by the catalysts at the conditionsused in the process. In general, the suitability of a petroleum oil asfeed declines as the parafiin content increases. Preferred petroleum oilfeeds are partially refined lube oil stocks, such as bright stocks,neutrals, and rafiinates of naph- -thenic crude.

Crude lube cuts from highly naphthenic crude petroleum are alsosuitable, however, though the hydrogenated product may require milddewaxing.

.The nitrogen content of petroleum oils rich in polycyclic hydrocarbonsis present primarily as heterocyclic nitrogen compounds. Removal of thenitrogen improves the lube oil not only by eliminating the highlycolored nitrogen compounds, but. also by converting such hetprior artwhere 0.5-2 LHSV,fto obtain the technical reliable index-of thedegree ofcolor improvement is obtained The new concept of this denum-aluminacatalysts are unusually active for hydro- V genation of nitrogencompounds, the conditions used in the process of this invention arepeculiar to the catalysts, Although with these catalysts moremoderateconditions of temperature, pressure, and space velocity could beemployed to remove a specified fraction or are'einployedin theinvention, as compared to hydrofining processes ofthe only mildhydro-finishing was contemplated; V a

In .carrying out the catalytic hydrogenation of this invention anysuitable equipment arrangement may be used for contacting the oilwiththe catalyst in the presence of excess hydrogen. For example, thecatalyst may be maintained as one or more fluidized beds, gravitatingbeds, or fixed beds of small the oil and hydrogen are passed, upflow ordownfiow, concurrent or countercurrent.

oil may also be used. Usually, the catalyst is in the form of smallpellets or rod-hke'extrusions contained in' a reactor as several fixedbeds, and the oil and hydrogen are passed together downfiow through thebeds at con trolled temperature, pressure, and flow rates. Theefiluentis cooled to separate product oil from hydrogen-rich gas, whileis recycled.

or more standard cubic feet per barrel ally 2,00O-6,000 s.c.f./bbl.

The total pressure depends on the purity of the hydro-v such pressurescolor improvement is accomplished over a broad rangeof.temperatures,,from 600 F; to 800 F., permitting maximum flexibilityin control of the nitrogen removal. Preferred temperatures are between600 and 750 F. for the limited nitrogen removal desired in thisinvention, especially temperatures of 650'700 F.

Space velocities of 0.23 LHSV are used, preferably and "economicadvantages of adequate contacting time in equipment of 7 reasonabledimensions; At milder conditions of lower nitrogen'removal is a lesshydrogenation of thetoil; the advantages [gained by using thehigh metal'content,

pressure, i.e., below 800 p.s.i.,

' sulfided, 'nickel-molybdeuum-alumina catalysts are less pronounced,and the range of temperatures at is narrower.; invention, the method ofusing it, and the advantages obtained, thereby may be best explainedandunderstood by means of examples. In the following examples, wherereference is made to a which particles, through which- A slurry. ofcatalyst in,

To maintain a high hydrogen partial pressure and to insure that excesshydrogen is present, the hydrogen-to-oil ratio is from 1,000 to 10,000

(s.c.f./bbl.), ususulfided nickel-molybdenum 'percent of the nitrogencontent of an oil, 'in general higher pressures, above 800 psi,

Tab lel V V 1"? V Ralfinate yield Property Desired product 40% WGravity, API 21. 7 19. 19. 3 Vlscosity, SSU at; 100 F- 1, 688 2, 525 2,879 Viscosity, SSU at 210 IL -95- 86. 3 101 Color, A STM Less than 4 V 56.5 Pour point, F.-- Less than +10 10 +5 Natural oxidation Greater than7 12 4. 9 3. 6 stability, hours. V Catalyzed oxidation Greater than1.8.-. 1.9 0.8 0. 8

stability, hours. 7 Nitrogen, ppm 80D 1, 660 2, 400 AIQIJJ3-tl0$,percent 9 I I 15. 5

" bina'tion of mild solventextraction catalyst, the "catalyst employedwas prepared by impregnating a high purity alumina base. with nickelnitrate, calcining, then impregnating with'ammonium molybdate, andcalciniu'g, again impregnating with ammonium molybdate, and calcining.The oxide catalyst, which contained 6 nickel and 20% molybdenum, wassulfided by contactingwith hydrogen containingdimethylrlisulfide,equivalent 'on hydrogenation to 2% H 5, at about 500 F. to convert the,metal oxides substantially to the sulfides prior rouse in the catalytichydrogenation process. The first exampleillustrates an embodiment of theinvention in the production of low cold test lubricating oil of improvedcolor and oxidation stability from a naphthenic cr'ude by acom followedby catalytic hydrogenation at controlled conditions. L

EXAMPLE I i A naphthenic California crude was distilledto obtain,

a'heavy crude lube distillate amounting to about 8 volume percent'ofthecrude, and boiling from about 500 F. to

about 700 F. at 10 mm. Hg. The distillate was solvent; extraction atvarying solvent-to-oil;

treated by phenol ratios to obtain lube oil rafiina'tes' at volumetricyields of 40%, 60%, and 70%. Properties of therafiinates are listed in.Table'l. The 40% yield raflinate' representstlow cold test lube oilproduced by the prior art without catalytic hydrogenation; The 60% ofpoor quality with respect.

and 70% rafiinates are The 60% and 70% nickel-molybdenum catalyst atconditions controlled-to treating conditions used and tained are listedinTable l1.

NoTn.Natural oxidation stability is the time required for a givenvolumeof the oil, as is, to absorbfrom air bubbled through the oxidationinhibitor and the oxidation is This property Table II I ,7 l

Feed treated 60% Rattinate 70% Ratfiuate Congitions:

ressure, p.s.i.a. 112-; Temperature, F Space velocity, LHSV 1 40 Gasrate, s.c.f. Hz/bblu' 4 i300 Product properties:

Gravity, API 22 4 Viscosity, ssU at F 1 43s Viscosity, SSU at 210 F is 4a Color, ASTM 1' 5 Pour point, F 5 Natural oxidation stability, hou.rs 38 Catalyzed oxidation stab ty, hours. 2 5 Nitrogen, p.p.m 905 Percentnitrogen removal to color and oxidation stability, and have higher thanthe dsiredviscosity; rafiinates were then subjected to, catalytichydrog'enation by contacting with the sulfided oil, to absorb one literof oxygen at the same conditions T The catalytic hydrogenation ofExample I improved the color in every case and improved the oxidationstability of the rafiinates to the desired extent when the operatingconditions were controlled to remove 30-60% of the nitrogen content,with an optimum apparently at about 40-50% removal. The viscosoity,however, dropped more than would be desired. In a novel embodiment ofthe present invention, product lube oil of the desired viscosity isproduced at' greater over-all yield by starting with a crude lubedistillate of higher than the desired boiling range, solvent treatingthe distillate to obtain a high yield of raflinate of higher than thedesired viscosity and of poor quality with respect to color andoxidation stability, and then subjecting the rafiinate to catalytichydrogenation by contact with a high metal content, sulfided,nickel-molybdenum catalyst at conditions of temperature, hydrogenpartial pressure,

' and space velocity controlled in the ranges 650-750 F.,

at least 1500 p.s.i.a., and 0.5-3 LHSV, to remove 30- 60% of thenitrogencontent and thereby to adjust the color, viscosity, and oxidationstability to the desired Values. That an increased yield of superiorproduct is obtained thereby is illustrated by the following example.

EXAMPLE II The naphthenic crude of Example I was distilled to obtain abroader lube oil distillate amounting to about 9 volume percent of thecrude by including higher boiling material. The distillate was solventtreated by phenol extraction to obtain a poor quality lube oil raffinateat 60% yield. The raifinate was then subjected to catalytichydrogenation by contacting with the nickelmolybdenum catalyst at 2000p.s.i.a. hydrogen partial pressure, 675 F., and 1.3 LHSV, with 6700s.c.f. of H per barrel. Properties of the raflinate feed and the lubeoil product are given in Table III. Processing in this way increases theyield of product lube oil from crude by 47.5% as compared to the solventtreating method formerly used.

Table 111 Property Ratr'mate Product Gravity, API 20. 2 22. 5 Viscosity,SSU at 100 F--- 2, 774 1, 715 Viscosity, SSU at 210 F 1 3. 6 (3. 3Color, ASTM 8 1. 5 Pour point, F 0 Natural oxidation stability, hour 4.6 12. Catalyzed oxidation stability, hours- 0. 8 2. 1 Nitrogen, ppm 1,710 1, 050 Aromatics, percent 13. 5 Percent nitrogen removal 39 Theconditions of temperature, pressure, and space velocity may be alteredwithin limits to obtain the same fraction of nitrogen removal andthereby to obtain the same improved product. However, for the treatmentof rafiinates, the pressure should be relatively high, i.e., above 1500p.s.i.a. H preferably at least 2000 p.s.i.a. Lower temperatures may beused at lower space velocities, but we prefer for the best results touse a space velocity of at least 0.8. The temperature can then be in thepreferred range of 650-750 F. Ordinarily, the temperature is increasedover a period of time to compensate for catalyst deactivation. However,the conditions of Example II were maintained for over 1000 hours withoutany noticeable deactivation or catalyst fouling by coke deposits.

The invention may also be used to produce residual or non-distillatelube oils of improved color and oxidation stability, for example, brightstock. A high natural oxidation stability is a valuable property ofbright stock because such oils are used to a great extent inuncompounded lubricants. The present invention produces bright stock ofimproved color and having maximum oxidation stability by catalytichydrogenation of nitrogen-containing bright stock at conditionscontrolled with- 6 in the ranges 800-2000 p.s.i.a. hydrogen partialpressure, 600-7 00 F., and 0.5-3 LHSV, to remove 20-60% of the nitrogencontent. This is illustrated by the following example.

EXAMPLE III A bright stock boiling entirely above 300 F. at onemillimeter mercury absolute pressure was contacted with the sulfidednickel-molybdenum catalyst at 1000 p.s.i.a. H 650 F., 0.5 LHSV, and 6000s.c.f. H bbl. Proper- Similar results were obtained by catalytichydrogenation at 1000 p.s.i.a., 700 F., and 2.4 LHSV. At moresevere-conditions the oxidation stability is adversely affected; at mildconditions the oxidation stability is not improved.

As shown, the invention can also be used to improve the additiveresponse of bright stock, for example, to oxidation inhibitors. This isof particular value where the bright stock is to be used in compoundedlubricating oils such as high viscosity turbine oils.

A turbine oil comprising 40% bright stock was prepared using the productof Example HI. With 0.25 weight percent of a commercial oxidationinhibitor added, the turbine oil had a life of 2,140 hours in a turbineoil standard test.

From the foregoing, it is seen that the exact conditions of temperature,pressure, and space velocity to be employed in a particular case dependon the properties of the particular feed stock and the properties of thelube oil desired. Thus, for example, in the case of two petroleum oilsof similar boiling range but difierent nitrogen contents, the oil ofhigher nitrogen content will require somewhat more severe conditions toaccomplish the same percent removal of nitrogen as the lower nitrogencontent stock. However, these somewhat more severe conditions are foundto be required also to obtain the desired improvement in the lube oilproperties. This is illustrated by a comparison of the similar feeds ofExamples I and 11. Thus, with the particular objective of this inventionin mind, and having the examples herein before him, one skilled in theart will, with but minimal experimentation to verify the estimates, beable with reasonable accuracy to predict the appropriate conditions touse with the sulfided nickel-molybdenum catalysts to obtain a desiredlube oil product. Hence, the examples themselves are not to beconsidered limiting, and the true scope of the invention is defined bythe following claims.

We claim:

1. A process for producing lubricating oil of improved color and naturaloxidation stability which comprises sol vent refining a heavy petroleumoil to obtain a solventrefined lubricating oil fraction rich inpolycyclic hydrocarbons, containing heterocyclic nitrogen compounds andhaving poor color above 4.5 on the ASTM scale and poor natural oxidationstability,

hydrogenating said solvent refined fraction by contacting in thepresence of excess hydrogen with a sulfided nickel-molybdenum-aluminacatalyst containing between 4 and 10 weight percent nickel and between12 and 30 weight percent molybdenum at reaction con ditions in theranges 800-3000 p.s.i.a. hydrogen partial pressure, 600-750 F, and 0.2-3LHSV, While controlling the reaction conditions in a narrow range jcarrying out the solvent refining of said within said ranges appropriatefor the particular sol- Vent-refined fraction to obtain only partialremoval I amounting tobetween 30% and 60%- of the nitrogen from'said'oil, i a

and recovering as the product hydrogenated lubricating oil havingimproved color below 4.5 on the ASTM scale and improved naturaloxidation stability.

, 2. The processof claim 1 wherein said heavy petroleum 7 ''oil is aresidual petroleum oil, which 'is solvent refined to obtain'as saidsolvent-refined lubricating oil fraction a bright stock, and thereaction conditions are controlled during contacting said brightrstockwith said sulfided cata .lyst within the ranges 8002000 p.s.i.a.hydrogen partial pressure, 600700 F., and 0.5-3 LHSV.

i 3. A process in accordance with claim ,1 wherein said flheavypetroleum oil is a heavy vacuum distillate of naphthenic crude petroleumrfrom -which distillate there is recoverable by phenol extraction araifinate of desired viscosity having acceptable color and oxidationstability only if limited to a rafiinate yield of less than 50% byvirtue of said distillate having a higher average'boiling point thandesired 'for said raflinate,

distillate to obtain as said solvent-refined lubricating oil fractionazrafiinate of poor'color and oxidation stability in greater than 50%yield and having higherthan desired viscosity, controlling the reactionconditions during said hydrogenating' in the ranges 1500-3000 750 F.,and 0.5-3

p.s.i.a. hydrogen partial pressure, 650- LHSV, and recovering as saidproduct which comprises '7 yield than is obtainable from the low coldtest lubricating oilof the desired viscosity'having improved color andoxidation stability in a greater naphthenic crude by dis tillation andextraction. i I y a .4. The process of claim 3 wherein the reactioncondi; tions during-said hydrogenating are controlled in the ranges2000-3000 p.s.i.g., 650-750 F,. and O.8 3'LHSV to limit the removal ofnitrogen compounds to between 40% and and thereis recovered as theproduction; cold test lubricating oil having a color below 4 on, theASTM'scale and a natural oxidation stability greater. than 7hours. '7 rPteterences Cited by the Examiner UNITED STATES PATENTS 2,706,167 7 4/Harper et al. 208-264 2,905,625 9/59 Berger; 20s 254 2,905,636 9/59Watkins et a1. 208-254 2,944,006 7/60' Scott 20889 2,983,676 5/61Howland 20s 2s4 2,988,501 6/61 Inwood r 208-254 7 3,004,913 10/61 Tucker208 544- 3,014,860 12/61 Douwe s et al. 208 254' 3,046,218 7/62 Henke etal. 208 14'4' 3,094,480 6/63 Richardson 208"143 3,105,813 10/63Gtltberlet 208 254 3,114,701 12/63 Jacobson et al 200-254;

'ALPHoNso D. SULLIVAN, Primary Examiner. V

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,189,540 June 15, 1965 Robert H. Kozlowski et a1,

It is hereby certified that error appears in the above numbered patentreqliring correction and that the said Letters Patent should read asoorrected,below.

Column 1, line 17 for "alumnia" read -alumina column I5, line 30, for"while" read H which column 6, line 37, after "testq" insert With normalbright stock the life is 940 hours.

Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Altusting Officer Commissioner ofPatents

1. A PROCESS FOR PRODUCING LUBRICATING OIL OF IMPROVED COLOR AND NATURALOXIDATION STABILITY WHICH COMPRISES SOLVENT REFINING A HEAVY PETROLEUMOIL TO OBTAIN A SOLVENTREFINED LUBRICATING OIL FRACTION RICH INPOLYCYCLIC HYDROCARBONS, CONTAINING HETEROCYCLIC NITROGEN COMPOUNDS ANDHAVING POOR COLOR ABOVE 4.5 ON THE ASTM SCALE AND POOR NATURAL OXIDATIONSTABILITY, HYDROGENATING SAID SOLVENT REFINED FRACTION BY CONTACTING INTHE PRESENCE OF EXCESS HYDROGEN WITH A SULFIDEDNICKEL-MOLYBDENUM-ALUMINA CATALYST CONTAINING BETWEEN 4 AND 10 WEIGHTPERCENT NICKEL AND BETWEEN 12 AND 30 WEIGHT PERCENT MOLYBDENUM ATREACTION CONDITIONS IN THE RANGES 800-300 P.S.I.A. HYDROGEN PARTIALPRESSURE 600-750*F., AND 0.2-3 LHSV, WHILE CONTROLLING THE REACTIONCONDITIONS IN A NARROW RANGE WITHIN SAID RANGES APPROPRIATE FOR THEPARTICULAR SOLVENT-REFINED FRACTION TO OBTAIN ONLY PARTIAL REMOVALAMOUNTING TO BETWEEN 30% AND 60% OF THE NITROGEN FROM SAID OIL, ANDRECOVERING AS THE PRODUCT HYDROGENATED LUBRICATING OIL HAVING IMPROVEDCOLOR BELOW 4.5 ON THE ASTM SCALE AND IMPROVED NATURAL OXIDATIONSTABILITY.